Russian President Dmitry Medvedev has signed nuclear and defence agreements worth billions of dollars during a two-day visit to India.
He has met Indian PM Manmohan Singh in Delhi on a trip that saw handshakes on the joint development of a so-called fifth generation stealth fighter jet.
There was also an agreement to supply more Russian nuclear power reactors.
All five permanent UN Security Council members have now made trade-focused visits to India in recent months.
The BBC's Mark Dummett in Delhi says the visits are a sign of India's growing clout on the world stage. As recession bites elsewhere, India is booming, he points out.
A Cold War ally and for many years the default weapons supplier to India, Russia has faced tough competition from Europe and the US for a slice of Delhi's booming defence market.
Wary of its rising regional rival, China, India is now one of the world's largest buyers of fighter jets, tanks, submarines and other defence equipment. BBC News
